Scalable integral fan motor assembly

ABSTRACT

An improved air moving device that is scalable for use in a variety of applications requiring different fan sizes. The fan includes a number of fan blades, each having a discrete magnet mounted thereon. The orientation of each magnet is such that the direction of the magnetic field alternates from one blade to the next. The outside edge of each blade is metalized in a way that the magnetic field is present across the entire outer edge of the fan blade. In an alternate embodiment the fan blade assembly includes fan blades fabricated of a ferrous material in which the tips of the blades are magnetized through exposure to a strong magnetic field after fabrication of the blade assembly. The configuration of the blades in both embodiments enables the differential in field strength to assist with the rotation of the fan blades.

FIELD OF THE INVENTION

[0001] The present invention relates generally to an air movingapparatus and, more particularly, to a fan for cooling electronicequipment with improved reliability and increased scalability.

BACKGROUND OF THE INVENTION

[0002] A wide variety of equipment and systems, such as portable anddesktop computers, mainframe computers, communication infrastructureframes, automotive equipment, etc., include heat-generating componentsin their casings. As increasingly dense and higher performanceelectronics are packaged into smaller housings, the need for effectivecooling systems is paramount to prevent failure of such sensitiveelectronics devices. One method used to remove heat from such equipmentis to have an axial fan draw air from the exterior, of the casing toblow cooling air over the heat-generating components. However, as thenumber of electronics devices in offices and households increases, sotoo does the number of cooling fans. As such, fan noise becomessignificantly loud and undesirable.

[0003] Typically, known fan assemblies include a fan blade structure,fan housing and a discrete motor. The fan motor is centrally mounted tothe housing and the fan blade assembly is attached to the shaft of themotor. These types of fan assemblies are susceptible to a variety offailures. For example, the reliability of the motor used in the fanassembly may be compromised due to the heat generated by the motor orthe heat of the surroundings in which the motor operates. Similarly, theheat affecting the motor also may affect the life of the fan bearings,resulting in premature failure of the fan. Another disadvantage ofexisting fan assemblies is the noise generated by these devices. As thedensity of electronics devices increases and as increasing numbers oftransistors are packed into CPU cores, increased cooling becomesparamount. Generally such increased cooling comes at cost in the form ofincreased noise. Fans may be required to be bigger, thereby requiringnoisier higher torque motors. Or, higher rotational speeds may berequired, resulting in noisier motors. Alternatively, multiple fans maybe used, which also results in increased noise due to the multiplemotors in operation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0004]FIG. 1 is a front view of an air moving apparatus in accordancewith the present invention showing a tube axial fan including fan bladeswith metalized edges and permanent magnets mounted thereon;

[0005]FIG. 2 is a side cross-sectional view of a fan housing showing thefield coil and field core in accordance with the present invention;

[0006]FIG. 3 is a front cross-sectional view of the air moving apparatusof FIG. 1 showing the field coil and field core in accordance with thepresent invention;

[0007]FIG. 4 is a side cross-sectional view of the fan housing showingthe field coil, field core and blade in accordance with the presentinvention;

[0008]FIG. 5 is an operational state diagram of the fan with the bladesin motion in accordance with the present invention; and

[0009]FIG. 6 shows multiple front cross-sectional views of fan housingsof varying sizes showing the field coil and field core in accordancewith the present invention

DETAILED DESCRIPTION

[0010] The present invention is directed to an improved air movingdevice, such as a fan, that is scalable for use in a variety ofapplications requiring different fan sizes. In a first embodiment, thefan includes a number of fan blades, each having a discrete magnetmounted thereon. The orientation of each magnet is such that thedirection of the magnetic field alternates from one blade to the next.Furthermore, the outside edge of each blade is metalized in a way thatthe magnetic field is present across the entire outer edge of the fanblade. In another embodiment, the fan blade assembly includes fan bladesfabricated of a ferrous material in which the tips of the blades aremagnetized through exposure to a strong magnetic field after fabricationof the blade assembly. Advantageously, in both embodiments, theconfiguration of the blades is such that that the differential in fieldstrength assists with the rotation of the fan blades.

[0011] In each embodiment described above, the fan housing includes afield coil, which is integrated into the fan housing. The core of thefield is constructed of a flexible laminate that allows it to be placedaround the circumference of the housing after the windings have beenattached. A particular advantage of the present embodiment is that onlya single coil is needed, rather than two or more, for operating themagnetic fan. Additional coils may be added, but are not necessary,thereby reducing the cost and weight of the fan.

[0012] Referring to FIG. 1, there is illustrated an air moving apparatus100 in the form of a fan 105 mounted in a housing 102 havingthrough-holes 112 for receiving a screw or other fastening device formounting purposes. The fan 105 includes a hub 106. Not shown is thecenter of the hub 106 mounted on one end of a ball-bearing axle and theother end of the ball-bearing axle mounted in a holder in the center ofthe fan housing 102 to provide an axis of rotation. Several fan blades104 a-104 d are mounted evenly around the hub 106. Each fan blade 104a-104 d is formed or mounted with a metalized strip 108 a-108 d thatextends the entire length of the outside edge of the fan blade. Adiscrete permanent magnet 110 a-110 d is mounted on each fan blade 104a-104 d such that the magnetic field created by the magnet 110 a-110 dis present through the metalized strip 108 a-108 d. Each magnet 110a-110 d is oriented such that the direction of the magnetic fieldalternates between successive blades. In an alternate embodiment, thefan blades 104 a-104 d are formed using a ferrous material where thetips of the fan blades are magnetized through exposure to a strongmagnetic field after the blade assembly is fabricated. A particularadvantage of such an embodiment is the reduced cost realized fromeliminating the need for mounting discrete magnets and metalized stripson each fan blade.

[0013] Referring to FIG. 2, the air moving apparatus 100 is illustratedfrom the side. As shown, the housing 102 is formed or molded with anaperture for housing an integrated field core 116 and a field coil 114.The field core 116 is constructed from a flexible laminant materialaround which the windings of the field coil 114 are wound. The fieldcore 116 includes two faces 118, 118′ (FIG. 3). Using the flexiblelaminant material allows the field core 116, 118 to be placed around thecircumference of the housing 102 after the windings have been attached.

[0014]FIG. 3, more clearly illustrates the orientation of the field coil114 and field core 116 and field core faces 118, 118′ within the housing102. In particular, the field core faces 118, 118′ are oriented inwardstoward the outer edges of the fan blades 104 a, 104 b. The length, pitchand curvature of the field core faces 118, 118′ are such that the fieldcore extends from just past the leading edge of one fan blade 104 a tojust past the trailing edge of the adjacent fan blade 104 b. Further,the field core pitch is such that there is a continuous magnetic fieldbetween the fan blades. Power is supplied to the field coil 114 throughwire leads (not shown) leading to the field coil 11. This 4creates anelectromagnetic circuit for use in powering the fan 105. The higher thecurrent through the field coil 114, the stronger the magnetic field is.Thus, the rotational speed of the fan 105 is adjusted by adjusting thevoltage supplied to the field coil 114. A particularly effective voltagerange is between 20VDC and 32VDC. The voltage may also be scaled down to12VDC for use in personal computers as case fans or CPU and/or chipsetcooling fans.

[0015] Known DC motors typically include a stator, rotor assembly, rotorposition sensor and a commutation control chip. The stator is a wound,stationary set of electromagnets typically connected to the fan housing.The rotor assembly includes an iron core with permanent magnetic polesthat is assembled into the hub of the fan. The rotor assembly isattached to an axle that rides on a pair of bearings in the fan frame toallow the rotor's permanent magnets to rotate freely around the outsideof the stator. A known Hall-effect device is used to sense the rotorposition. The commutation control chip uses the signal from theHall-effect device to time the switching of each stator phase. Thus, arotating electromagnetic field is established around the stator.Accordingly, the rotor is set in motion by the magnetic coupling betweenthe rotating electromagnetic field and the magnetic pole.

[0016] Although the present invention is unique in its configuration andconstruction, and differs significantly from the fans found in the art,for ease of understanding certain parallels maybe drawn between existingfan designs and the present invention. For example, referring once againto FIG. 3, the housing 102 of the present invention having the mountedfield coil 114 and field core 116 maybe considered the stator of theconventional motor. Similarly, the fan blades 104 a-104 d having themagnetized tips maybe considered the poles of a conventional motor.Thus, the number of fan blades in the present invention generallycorresponds to the number of poles in the conventional motor. AHall-effect sensor (not shown) is mounted at a 90 degree orientationfrom the electromagnetic circuitry. The Hall-effect sensor causes aparticular polarity through the field core faces 118, 118′ that is usedto attract the first fan blade 104 a and also is used to detect the nextfan blade 104 b. The polarity may then be switched to repel the firstfan blade and attract the next fan blade.

[0017] Referring to FIGS. 4-5, the operation of the fan in the presentinvention is shown in detail. As illustrated, the fan housing 102includes the integrated field core face 118, field core 116 and fieldcoil 114. A voltage source (not shown) provides a pulse to the fieldcoil 114. The pulse causes magnetic attraction of the fan blade 104 a tothe center of the field core face 118. As the fan blade 104 a approachesthe center of the field core face 118, the Hall-sensor determines theposition of the blade 104 a. As shown in FIG. 5, as the blade 104 aapproaches the field core face 118 and is attracted to its center, theHall-sensor causes the polarity of the field core 116 to be switched, orreversed. As such, the blade 104 a that is directly in front of thefield core face 118 and was previously attracted to the center of thefield core face 118 is now repelled away from the field core face 118and the next, or adjacent, fan blade 104 b is attracted to the center ofthe field core face 118. This process repeats for fan blade 104 c andsubsequent fan blades, thereby causing the fan 105 to rotate. Increasingthe strength of the pulse by using a larger voltage source creates astronger magnetic field in the field core. This increases the rotationalspeed of the fan. Furthermore, the magnetic field is stronger towardsthe middle of the fan edge and the field core and weaker on theperimeter. The differential in the field strength assists with therotation of the fan. Alternatively, tapering the edge of the fan bladewith respect to the housing also may be used to create a similardifferential in field strength.

[0018] Another advantage of using the flexible laminant is that the samefield core 116, 118 can be used for a variety of different fan sizes, asillustrated in FIGS. 6-8. Thus, increased scalability is gained byenabling the same field core to be used, for example, in micro fans forsmall electronics devices to large fans for cellular base stations.

[0019] Referring to FIG. 6, the present invention is shown in anembodiment wherein the air moving device 101 includes a housing 122 forhousing a fan 125, for example, that is 1.5 inches in diameter. The fan125 is configured with a hub 129 and four fan blades 115 a-115 d. Thefan housing 122 is formed with the same electromagnetic circuitry havingfield core 116, field core face 118 and field coil 114 assembly, asdescribed above. As shown, the fan blades are sized such that two fanblades 115 a, 115 b are within the span of the field core 116 and fieldcore face 118. Accordingly, the operation of the fan is substantiallysimilar to that described above.

[0020] Turning now to FIG. 7, the same electromagnetic circuitry isshown as being used once again in an air moving device 123. In thisexample, however, the fan 129 is two inches in diameter and is installedin a correspondingly larger housing 124. As shown, to enable aconfiguration where two fan blades 126 a-126 b are within the span ofthe field core 116 and field core face 118, the hub 127 is increased indiameter so that there is little change in the blade size. It is to benoted that alternative configurations of the fan are possible where onlytwo fan blades fall within the electromagnetic circuitry.

[0021] Referring to FIG. 8, an exemplary air moving device 132 having afan 135 that is 2.75 inches in diameter is shown. As illustrated, thehub 137 is increased in size even further relative to the previouslydescribed fans. By doing so, once again only two fan blades 136 a and136 b fall within the span of the field core 116 and field core face118.

[0022] While there have been illustrated and described particularembodiments of the present invention, it will be appreciated thatnumerous changes and modifications will occur to those skilled in theart, and it is intended in the appended claims to cover all thosechanges and modifications which fall within the true spirit and scope ofthe present invention.

What is claimed is:
 1. An air moving apparatus, comprising: a fanhousing; a fan having a rotatable hub and plurality of blades adjacenteach other mounted to the hub for rotation about an axis of rotation toprovide pressurized airflow out from the housing, each blade having amagnetic tip end portion for producing a magnetic field, wherein eachadjacent blade has an opposite magnetic orientation to the other; and afield coil mounted to the housing for attracting and repelling a firstblade and subsequently attracting and repelling each adjacent blade toenable the fan to rotate about the axis of rotation.
 2. The air movingapparatus of claim 1, wherein the field coil comprises a core.
 3. Theair moving apparatus of claim 2, wherein the core is a flexible laminantfor enabling the field core to be placed around a circumference of thefan housing subsequent to the mounting of the coil.
 4. The air movingapparatus of claim 2, wherein the core is a flexible laminant forenabling the field core to operate with fans of various sizes.
 5. Theair moving apparatus of claim 1, further comprising a hall effect sensorfor sensing the orientation of the magnetic field of the blades.
 6. Theair moving apparatus of claim 4, wherein the field of the coil isreversed when the hall effect sensor senses a reversal in theorientation of the magnetic field when an adjacent blade is detected. 7.The air moving apparatus of claim 1, wherein the magnetic tip endportion of each blade comprises a metalized strip and permanent discretemagnet mounted on the tip end portion for enabling the magnetic field tobe present across the entire tip end.
 8. The air moving apparatus ofclaim 1, wherein each fan blade is formed of a ferrous material and hasa magnetized tip end portion.
 9. A method for integrating a motor unitinto a fan assembly, comprising: providing a fan housing having anannular wall extending about a predetermined number of blades of thefan; magnetizing the tip end portion of each fan blade such that eachadjacent blade is in opposite magnetic orientation to the other;mounting a field coil having a core into the housing; energizing thefield coil in a first orientation for enabling the core to attract afirst fan blade to the center of the core's face; and energizing thefield coil in a second orientation that is the reverse of the firstorientation for enabling the core to repel the first fan blade andattract an adjacent fan blade.
 10. The method of claim 8, furthercomprising the step of determining the position of each fan blade fordetermining when the field coil energization is to be switched from thefirst orientation to the second orientation.
 11. The method of claim 8,wherein a hall effect sensor determines blade position.
 12. The methodof claim 8, further comprising the step of orienting the face of thecore to extend from slightly beyond the leading edge of the first fanblade and slightly beyond the trailing edge of the adjacent fan blade.13. The method of claim 8, further comprising the step of forming thecore from a flexible laminant for enabling the core to operate with fansof various sizes.
 14. The method of claim 8, further comprising the stepof forming the core from a flexible laminant for enabling the core to bemounted around the circumference of the fan housing subsequent to themounting of the coil.
 15. The method of claim 8, wherein the magnetizingstep comprises mounting a metalized strip on the tip end portion of eachblade and also mounting a permanent discrete magnet on the tip endportion for enabling the magnetic field to be present across the entiretip end.
 16. The method of claim 8, wherein the magnetizing stepcomprises forming the fan blades of a ferrous material and magnetizingthe tip end portions
 17. An air moving apparatus comprising: a fanhousing; a rotatable hub; and a plurality of blades adjacent each othermounted to the hub for rotation about an axis of rotation to providepressurized airflow out from the housing, each blade having a magnetictip end portion for producing a magnetic field across the outside edgeof the blades, wherein each adjacent blade has an opposite magneticorientation to the other.
 18. The air moving apparatus of claim 17,further comprising magnetic circuitry integrated within said housing forattracting and repelling the plurality of blades to enable the fanblades to rotate about an axis of rotation.
 19. The air moving apparatusof claim 18, wherein the magnetic circuitry comprises a field coil. 20.The air moving apparatus of claim 19, wherein the field coil comprises acore.
 21. The air moving apparatus of claim 20, wherein the core is aflexible laminant.